This section provides background information related to the present disclosure which is not necessarily prior art.
Emission regulation requirements are mandating that engines have exhaust after-treatment systems to eliminate, or at least substantially minimize, the emission of, for example, particulate matter and NOx. To eliminate or reduce the emission of particulate matter and NOx, exhaust after-treatment systems can include components such as a particulate filter (e.g., a diesel particulate filter (DPF)), a selective catalyst reduction (SCR) component, and a diesel oxidation catalyst (DOC) component.
SCR and DOC components generally work in conjunction with reductant dosing systems that dose a reductant into the exhaust stream to treat the exhaust before the exhaust enters the SCR or DOC components. In the case of SCR, a reductant solution including urea is dosed into the exhaust stream before entry into the SCR component. In the case of DOC, a hydrocarbon reductant such as diesel fuel is dosed into the exhaust stream before entry into the DOC component.
The dosing systems for each of SCR and DOC exhaust after-treatments involve the integration of dosing modules, pumps, filters, regulators, and other necessary control mechanisms to control the dosing of each of these reductants into the exhaust stream. What distinguishes each of these systems is that hydrocarbon reductants do not freeze, while aqueous urea reductants can freeze in cold temperatures. A urea reductant dosing system, therefore, may require various components or configurations that assist in preventing the urea reductant from freezing in the dosing system, which can damage components of dosing system, or prevent the dosing system from properly dosing the urea reductant into the exhaust stream.